Power amplifiers are widely used in various communication networks to set the transmission power level of an information-bearing signal transmitted by one device to another device. For example, power amplifiers are used to set the pulse energy emitted by pulsed lasers in optical communication networks. Power amplifiers are also used in the radio frequency (RF) front end components of wireless carrier network devices—such as base stations, repeaters, and mobile client devices (e.g. mobile phones, smartphones, tablet computers, etc.)—to set the power level of a wireless signal transmitted through an antenna. Power amplifiers are also used in local area networks of homes and offices to support both wired and wireless connectivity of servers, computers, laptops, and peripheral devices such as photocopiers and printers.
In a mobile device relying on a battery, managing the operation of a power amplifier is of interest because the efficiency of the power amplifier is often a significant factor in the overall efficiency of the RF front end, and in turn, the battery life of the mobile device. Additionally, in part because of the high power levels at which a power amplifier operates relative to the other components in the RF front end, a power amplifier can cause device failure when the power amplifier is not prevented from drawing excessive current and/or causing a voltage spike, both of which can reach destructive levels.
In order to set the operating conditions for efficient operation, a preferred current draw of a power amplifier can be, in part, initially set by impedance matching the power amplifier to the antenna (or other transmission load), so that the power amplifier operates within a designed quiescent range set by bias circuitry. However, even when a power amplifier is impedance matched to an antenna, the power amplifier may draw excessive current and/or cause a voltage spike when subjected to unanticipated antenna load conditions. Consequently, battery life is reduced and device failure may occur if the excessive current and/or cause a voltage spike reach destructive levels.
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